Efficacy of continuous treatment with astemizole (Hismanal) and terfenadine (Seldane) in ragweed pollen-induced rhinoconjunctivitis

Astemizole (Hismanal; Janssen Pharmaceutica Inc., Mississauga, Ontario, Canada) and terfenadine (Seldane; Merrell Dow Pharmaceuticals Canada], Inc., Concord, Ontario, Canada) were compared for clinical efficacy in a double-blind randomized trial during the ragweed pollen season. Sixty adults, with a history of ragweed-induced rhinoconjunctivitis, were matched according to sensitivity to ragweed pollen. Half took astemizole, 10 mg/day, and the rest took terfenadine, 60 mg twice daily. Medications were started 1 week before and continued daily until 1 week after the ragweed pollen season (7 weeks). If the trial medication was insufficient to keep symptoms well controlled, a steroid nasal spray and/or eye drops were used in the minimum dose that would ensure symptoms were not troublesome. Subjects completed a diary of nocturnal and daytime nasal and eye symptoms and recorded the amount of concomitant medications used. Astemizole showed greater efficacy than terfenadine in controlling rhinorrhea; in addition, the astemizole group used less nasal spray. Other nasal symptoms, eye symptoms, and use of eye drops were similar in the two groups. Skin test sensitivity to serial dilutions of histamine and ragweed extract was determined 1 and 7 weeks after the start of the trial medication. More tachyphylaxis to histamine was shown by the subjects taking terfenadine, as demonstrated by a larger increase in skin sensitivity over the study period. However, a similar change was not observed for ragweed skin sensitivity. These results suggest that when the medication is started before and continued daily throughout the pollen season, astemizole is more efficacious than terfenadine in controlling nasal symptoms, but there is little difference for eye symptoms.(ABSTRACT TRUNCATED AT 250 WORDS)